Optical fibers in general are known in the art, and typically comprise a transparent core of a suitable glass or plastic material which is contained within a cylindrical cladding having an index of refraction less than the refractive index of the core. A plastic jacket or coating protects the fiber on the outside. When a light signal is focused upon one end of the fiber, the fiber core functions as a waveguide to transmit or propagate the light signal through the core with relatively small internal intensity losses and negligible transmission of the signal to the cladding. An important feature of this type of optical fiber is that gradual turns or bends in the fiber have little or no effect upon transmission of the light signal. Fiber optic cables may consist of a single fiber or many optical fibers. Each fiber is an independent optical waveguide in its operation by containing and transmitting signals completely, radiating virtually no external optical energy.
It may be necessary in installing and/or servicing fiber optic networks to be able to measure insertion loss within an optical network. Insertion loss within an optical network should be determined to be within acceptable limits in order to verify proper physical contact between adjoining optical fibers and to maintain the system loss budget. Currently, one specified way of determining insertion loss is with the use of a hand-held optical loss test set, which measures the insertion loss through a length of optical fiber that may include one or more joining points between adjoining optical fibers.